This invention relates to unsaturated polyester resins containing a small but effective amount of a dicyclopentadiene concentrate and laminates prepared from them. More specifically, the invention relates to polyester resins produced by reacting a glycol, an olefinically unsaturated dicarboxylic acid or anhydride, a saturated dicarboxylic acid or anhydride and an effective amount of a dicyclopentadiene concentrate having as the main reactive components about 60 to about 90 percent by weight dicyclopentadiene, about 5 to about 30 percent by weight of the mixed Diels Alder dimers or adducts of diolefins such as butadiene, piperylene, isoprene, cyclopentadiene, and methyl cyclopentadiene.
It is well known from the report by P. L. Smith, et al. "The Use of Dicyclopentadiene in Polyesters", Proceedings of the 22nd Annual Technical Conference, S.P.I., Reinforced Plastics Division, Washington, D.C. (1967) and the article by R. Zimmerman, et al. "Modification of Unsaturated Polyesters with Dicyclopentadiene", Fette-Seifen-Anstrichmittel 66, No. 9, 670-678 (1964), and U.S. Pat. No. 3,347,806 that polyesters can be modified with a concentrated dicyclopentadiene extract.